1. Field of the Invention
The present invention relates to the testing of printed circuit boards, and more specifically the testing of circuit boards by administering one or more electrical tests under automated control and distinguishing between passed and failed circuit boards.
2. Background of the Invention
Circuit boards, i.e., printed circuit boards or PCBs, in general may be tested by administering electrical tests during manufacturing. For example, U.S. Pat. No. 6,396,295 teaches a method of administering a test to an integrated circuit and determining whether the integrated circuit passes or fails the test.
The evolution and advancement of circuit board and electronic technology has brought about the need for new or additional tests that may be difficult, or impossible, with existing testing equipment. Many tests may be conducted by human operators because no existing automated equipment may be able to conduct the required tests.
For example, technologies such as planar magnetics may require inductance testing using ferrite cores and high voltage potentials, e.g., 2,000 volts or more. Existing automated testing equipment, e.g., flying probe testers and bed-of-nails testers, may not be capable of testing at high potentials and with cores. In addition, existing testing equipment may not be fully automated and may require human operators to perform one or more steps for each circuit test, which may lower overall manufacturing and testing efficiency. For example, a human operator may be able to test only 1,000 to 2,000 planar magnetic circuit boards per day for inductance and high potential while production needs may be 100,000 to 300,000 circuit boards per day.
Existing testing methods may be so time consuming and expensive so that, in order to be cost effective, only samples of lots and not each individual circuit board may be tested. One to three hundred defective circuit boards may be missed for every million defective circuit boards that are identified. Since, for example, a single circuit board design may be produced, currently at global levels, in quantities of 100 million or more per year, 10,000 or more defective circuit boards may be allowed to pass though quality review and then further processed, used, or sold to manufactures and end-users.
Each defective circuit board allowed though testing, processing, and eventually sold may require hours of the end-manufacturer's or end-user's time identifying and repairing the problem, potentially costing much more in lost productivity than the production cost of the original defective board.
What is needed is a system for more effectively and more economically testing circuit boards.